I want to store my 24 word mnemonic seed in 2 separate physical locations for safety reasons.

I separated the words in 2 groups of 12 with this algorithm:

- place all 24 words in group 1
- select random 12 words from group1, put them into group2 and replace them with placeholders in group1

I kept the order of the words. So to restore the original seed, you just need to fill the placeholders in group1 with words from group2 (in the same order).

My question is: is this safe? If a potential criminal got a hold of group1 or group2, would it be possible for them to determine the whole seed without the other group?